1. Field of the Invention
This invention relates to a centrifuge or a centrifugal separator having the function of detecting information about a rotor therein.
2. Description of the Related Art
General centrifuges or centrifugal separators include rotors into which samples to be analyzed are placed. The rotors are rotated at high speeds. In most centrifuges, rotors are replaceable. Regarding these centrifuges, a user can select a rotor of a type best suited for a sample to be analyzed. The maximum allowable rotational speed varies from rotor to rotor.
In general, identification (ID) information is used which represents the maximum allowable rotational speed of a rotor or the type of the rotor. A typical speed control technique includes a step of detecting ID information, a step of deriving the maximum allowable rotational speed of a rotor from the detected ID information, and a step of preventing the actual rotational speed of the rotor from exceeding the maximum allowable rotational speed.
Japanese utility-model publication 3-34279 discloses that two magnets are provided on each centrifuge rotor. The angular interval between the two magnets is predetermined according to the rotor type. During rotation of a rotor in a centrifuge, the angular interval between the two magnets is measured by a magnetic sensor, and the rotor type is detected on the basis of the measured angular interval. It is known that the angular interval between the two magnets is predetermined according to the maximum allowable rotational speed of the rotor.
U.S. Pat. No. 5,382,218 corresponding to Japanese patent application publication number 6-198219 discloses that on each centrifuge rotor, there are prescribed points spaced at equal angular intervals. A magnet is present in or absent from each of the prescribed points so that the rotor has a predetermined magnet presence/absence pattern. Different magnet presence/absence patterns are assigned to different rotor types, respectively. The magnet presence/absence patterns are of a code used as rotor-type ID (identification) information. During rotation of a rotor in a centrifuge, the magnet presence/absence pattern on the rotor is measured by a plurality of magnetic sensors, and the rotor type is identified on the basis of the measured magnet presence/absence pattern.
Japanese patent application publication number 7-47305 discloses that a centrifuge rotor is provided with an arrangement of one south pole and at most seven north poles as rotor ID information. A centrifuge body has magnetic sensors for detecting the magnetic-pole arrangement to identify the rotor.
U.S. Pat. No. 4,551,715 corresponding to Japanese patent publication number 6-41956 discloses an apparatus for determining the actual speed and maximum safe speed of a centrifuge rotor. A single circular array of equally spaced coding elements of two clearly distinguishable types is attached to the rotor. A single detector responsive to the coding elements produces an output signal that varies in accordance with both the number and type of the coding elements. A first circuit network is responsive to the number of coding elements encountered per unit time, without regard to type, to produce an actual speed or tachometer signal. A second circuit network is responsive to the number of coding elements of each type encountered during each revolution of the rotor, without regard to the speed thereof, to produce a rotor identification signal that is indicative of the maximum safe speed of the rotor.
U.S. Pat. No. 4,772,254 corresponding to Japanese patent publication number 63-33911 discloses a centrifuge rotor having a carrier ring formed with 24 boreholes distributed uniformly over its periphery at a predetermined radial distance from the axis of rotation to receive permanent magnets. The magnets are so inserted that in some cases their south poles and in others their north poles extend outwardly away from the ring. The orientation of the magnets and/or their presence or absence permits use of a binary coding system (0 or 1) uniquely to identify each centrifuge rotor. Each of the 24 boreholes corresponds to 1 bit. The presence of a magnet in a borehole is assigned to a bit of xe2x80x9c1xe2x80x9d while the absence of a magnet therefrom is assigned to a bit of xe2x80x9c0xe2x80x9d. The arrangement of the 24 boreholes is divided into first, second, third, and fourth sectors having 4 bits, 7 bits, 4 bits, and 9 bits, respectively. Magnets in the first, second, and third sectors have their north poles extending outwardly. On the other hand, magnets in the fourth sector have their south poles extending outwardly. The 4 bits in the first sector indicate the year of the construction of the rotor. The 7 bits in the second sector indicate the serial number of the rotor. The 4 bits in the third sector indicate the type of the rotor. The 9 bits in the fourth sector indicate the maximum permissible speed of the rotor. In U.S. Pat. No. 4,772,254, the positions of permanent magnets are limited to the positions of the 24 boreholes. This positional limitation causes a smaller number of different states of rotor information which can be represented by the orientation of the magnets and/or their presence and absence.
It is an object of this invention to provide a centrifuge with a rotor having marks or identification elements representing rotor information which can be changed among many different states.
A first aspect of this invention provides a centrifuge comprising a rotor; a motor for rotating the rotor; at least three identification elements provided on the rotor and arranged along a circumference of a circle whose center coincides with an axis of rotation of the rotor, wherein an angular interval between prescribed two of the at least three identification elements indicates a maximum allowable rotational speed of the rotor, and one or more of the at least three identification elements indicates a type of the rotor; a sensor for detecting the at least three identification elements during rotation of the rotor, and outputting a signal representing results of said detecting; means for measuring the angular interval between the prescribed two of the at least three identification elements in response to the signal outputted from the sensor to detect the maximum allowable rotational speed of the rotor; and means for detecting the type of the rotor in response to the signal outputted from the sensor.
A second aspect of this invention is based on the first aspect thereof, and provides a centrifuge wherein the prescribed two of the at least three identification elements are one of adjacent twos of the at least three identification elements which is the greatest in angular interval, and the angular interval between the prescribed two of the at least three identification elements along a route having one or more others of the at least three identification elements indicates the maximum allowable rotational speed of the rotor.
A third aspect of this invention is based on the first aspect thereof, and provides a centrifuge wherein the prescribed two of the at least three identification elements are one of adjacent twos of the at least three identification elements which is the greatest in angular interval, and the angular interval between the prescribed two of the at least three identification elements along a route having one or more others of the at least three identification elements indicates the maximum allowable rotational speed of the rotor, and wherein the one or more others of the at least three identification elements indicate the type of the rotor.
A fourth aspect of this invention is based on the first aspect thereof, and provides a centrifuge wherein an angular interval between first given two of the at least three identification elements is greater than an angular interval between second given two of the at least three identification elements.
A fifth aspect of this invention is based on the first aspect thereof, and provides a centrifuge wherein each of the at least three identification elements comprises a magnet.
A sixth aspect of this invention provides a rotor for a centrifuge. The rotor comprises first, second, third, and fourth magnets arranged along a circumference of a circle; wherein an angular interval between the first and fourth magnets indicates a maximum allowable rotational speed of the rotor, and an angular interval between the first and second magnets and an angular interval between the second and third magnets indicate identification information of the rotor.
A seventh aspect of this invention provides a centrifuge comprising a rotor; a motor for rotating the rotor; first, second, third, and fourth magnets provided on the rotor and arranged along a circumference of a circle, wherein an angular interval between the first and fourth magnets indicates a maximum allowable rotational speed of the rotor, and an angular interval between the first and second magnets and an angular interval between the second and third magnets indicate identification information of the rotor; a magnetic sensor for detecting the first, second, third, and fourth magnets during rotation of the rotor, and generating a signal representing results of said detecting; means for measuring the angular interval between the first and fourth magnets in response to the signal generated by the magnetic sensor; means for detecting the maximum allowable rotational speed of the rotor in response to the measured angular interval between the first and fourth magnet; means for measuring the angular interval between the first and second magnets and the angular interval between the second and third magnets in response to the signal generated by the magnetic sensor; and means for detecting the identification information of the rotor in response to the measured angular interval between the first and second magnets and the measured angular interval between the second and third magnets.